Water extraction apparatus for papermaking machine

ABSTRACT

Water extracting apparatus for the Fourdrinier or felt section of a machine for making paper, cardboard, building boards and the like includes a support formed with a plurality of spacedly parallel, outwardly open grooves respectively receiving elongated contact units in conforming engagement. Each contact unit includes an elongated channel member of extruded aluminum alloy or stainless steel, and a plurality of contact sections of sintered aluminum oxide or silicon carbide abuttingly juxtaposed in the direction of unit elongation. The top faces of the sections are located in a common plane and their bottom faces are superimposed on the free edges of the channel flanges to close the channel cavity which is filled with a bonding material.

Umted States Patent 1191 1111 3,928,125

Poeschl Dec. 23, 1975 WATER EXTRACTION APPARATUS FOR 897,353 5/1962 United Kingdom 162/374 PAPERMAKING MACHINE 221,925 6/1962 Austria 673,790 11/1963 Canada 162/352 [75] Inventor: Rudolf Poeschl, Vienna, Austria [73] Assignee: Feldmuhle Anlagenund Produktionsgesellschaft mit beschrankter Haftung, Dusseldorf-Oberkassel, Germany [22] Filed: Dec. 13, 1973 [21] Appl. No.: 424,197

[30] Foreign Application Priority Data Dec. 18, 1972 Austria 10796/72 July 2, 1973 Austria 5820/73 152 US. Cl 162/352; 162/374 [51] Int. Cl. D21F 1/48 [58] Field of Search 162/352, 374, 363, 364

[56] References Cited UNITED STATES PATENTS 3,393,124 7/1968 Klinger et al. 162/352 3,497,420 2/l970 Clark [62/352 3,535,204 [0/1970 Truxa I 162/352 3,836,428 9/1974 McConaughy 162/374 X FOREIGN PATENTS OR APPLICATIONS 294,560 3/1971 Austria 162/374 Primary ExaminerRobert L. Lindsay, Jr. Assistant ExaminerRichard V. Fisher Attorney, Agent, or FirmHans Berman [57] ABSTRACT Water extracting apparatus for the Fourdrinier or felt section of a machine for making paper, cardboard, building boards and the like includes a support formed with a plurality of spacedly parallel, outwardly open grooves respectively receiving elongated contact units in conforming engagement. Each contact unit includes an elongated channel member of extruded aluminum alloy or stainless steel, and a plurality of contact sections of sintered aluminum oxide or silicon carbide abuttingly juxtaposed in the direction of unit elongation. The top faces of the sections are located in a common plane and their bottom faces are superimposed on the free edges of the channel flanges to close I the channel cavity which is filled with a bonding material.

9 Claims, 21 Drawing Figures US. Patent Dec. 23, 1975 Sheet 1 of5 3,928,125

US. Patent Dec. 23, 1975 Sheet2of5 3,928,125

US. Patent Dec. 23, 1975 Sheet 3 of5 3,928,125

U.S. Patent Dec. 23, 1975 Sheet 4 of5 3,928,125

US. Patent, Dec.23, 1975 SheetS 0f5 3,928,125

WATER EXTRACTION APPARATUS FOR PAPERMAKING MACHINE This invention relates to water extracting apparatus for a paper-type machine, such as the forming board, foils, suction covers or felt conditioning units of a machine in which paper, cardboard, or similar material is prepared by gradual removal of water from a suspension of solids in an aqueous liquid, hereinafter referred to as water, or white water, while the solids are supported on a screen. More particularly, the invention is concerned with water extracting apparatus in which the elements making contact with the screen consist of material having a hardness greater than 6 on the Mohs scale.

It was customary for a long time to make the covers of suction boxes and other water extracting apparatus in contact with the traveling F ourdrinier wire and felts of a paper-type machine from hard wood which had only moderate resistance to wear so as to require relatively frequent replacement. Moreover, as the wooden structure loses its initial smoothness, it causes deterioration of the wire screen, and the replacement cost; of such screens constitutes a significant part of the operating expense of a paper-type machine.

Later replacement of hard wood as a material of construction by synthetic resin compositions, such as low-pressure polyethylene, reduced the screen wear, but did not solve the problem of frequent replacement of the contact elements in the water extraction apparatus. More recently, such contact elements have been made of materials having a hardness greater than 6 on the Mohs scale, such as silicon carbide and sintered aluminum oxide, which resist wear by the traveling screen for a period comparable with the useful life -'of any other part of the paper or paper-type machine, and maintain their surface finish so well as to greatly increase the useful life of the Fourdrinier wire with which they are in contact. Similar advantages were achieved when the suction units of felt conditioners were surfaced with the hard materials which resist abrasion by fillerparticles normally deposited on the felts in the press section of the machine and cause much less damage to the felts than earlier contact elements for the water extraction apparatus of felt conditioners. The water extracting apparatus, both in the Fourdrinier section and the press section of a paper-type ma chine, must be as long as the machine is wide, and modern paper-type machines may have widths of twenty feet or more. It is not practical to make unitary contact elements of the preferred hard materials having the necessary dimensions, and such elements are normally assembled from longitudinally juxtaposed sections having individual lengths of less than two feet and abuttingly engaging each other. To avoid damage to the traveling screen or felt, the exposed top faces of the contact sections must be located in a common plane, and a step of even a fraction of a millimeter at the juncture of two sections would be deleterious. Manufacturers of paper machines are equipped with grinding and lapping machines capable of finishing assembled, long contact elements, but such machines are not available in otherwise well equipped large paper mills.

Many paper-type machines initially equipped with wooden or plastic contact elements in their water extraction apparatus are still in operation, and will remain in operation for a long time to come. Their contact elements are being replaced gradually by elements consisting of sections of hard ceramic or carbide material. The dimensions of the assembled water extraction apparatus are such as to make it impractical to assemble and finish the apparatus at the plant of the paper machine builder and to ship it in the assembled condition if several contact units are juxtaposed in the direction of wire or felt travel. If the sections are installed 0 individually at the paper mill, they need to be ground and lapped manually on the paper machine, an operation which consumes much time and labor, and is successful only when performed by specially trained personnel.

Attempts have been made to alleviate the problem of precisely aligning the contact faces newly installed on an existing machine (French Patents Nos. 1,557,414 and 2,099,119) but were not entirely successful.

A primary object of this invention is the provision of a contact unit for water extraction apparatus in the Fourdrinier or felt section whose contact element consists of a plurality of sections made of a material of great hardness, greater than 6 on the Mohs scale, which is capable of being assembled and finished in the plant of the paper machine maker, yet small enough to be shipped conveniently as ordinary freight, and capable of being installed in an existing paper-type machine in a very short time and with a minimal amount of labor which need not be highly skilled.

With this object and others in view, the invention provides an elongated contact unit which comprises an elongated channel member having a web part and two flange parts extending from the web part in a common direction The several parts of the channel member jointly bound a cavity which is open in a direction away from the web part, the open side of the cavity being defined between the respective free end portions of the flange parts. Contact sections of a material having a hardness greater than 6 on the Mohs scale are abut tingly juxtaposed in the direction of unit elongation. Their exposed top faces are located in a common longitudinal plane, and their bottom faces are superimposed on the free end portions of the flange parts so that they jointly close the open side of the channel cavity. A body of bonding material fills the cavity in contact with the channel member and the contact sections.

Water extracting apparatus of the invention includes a support formed with a plurality of elongated, spacedly parallel, transversely open grooves which respectively receive contact units of the afore-described type in conforming engagement in such a position that the contact sections are outwardly exposed.

Other features, additional objects, and many of the attendant advantages of the invention will readily become apparent'as the same becomes better understood by reference to the following detailed description of preferred embodiments when considered in connection with the appended drawing in which:

FIG. 1 shows a suction box cover of the invention in fragmentary perspective view and partly in side-elevational section;

FIG. 2 shows a contact unit in the cover of FIG. 1 in side elevational section on a larger scale;

FIGS. 3 to 7 show respective modifications of the unit of FIG 2 in corresponding views;

FIG. 8 illustrates a contact unit for a foil assembly in side elevational section;

FIG. 9 shows a contact unit for a forming board in side-elevational section;

FIG. 10 illustrates a modification of the device of FIG. 8 in a corresponding view;

FIG. 10A is a fragmentary, sectional view of a modification of the suction box cover of FIG. 1;

FIG. 11 illustrates another contact unit for a forming board in side-elevational section;

FIG. 12 shows a contact unit for a suction box cover similar to the unit of FIG. 11;

FIGS. 13 to 15 are side'elevational, sectional views of modifications of the device of FIG. 11;

FIG. 16 shows yet another modified contact unit for a forming board;

FIG. 17 illustrates another suction box cover of the invention in fragmentary, side-elevational section;

FIG. 18 shows the apparatus of FIG. 17 in top plan view without most of its contact units;

FIG. 19 illustrates the method of assembling of the apparatus of FIGS. 17 and 18 in a perspective view; and

FIG. 20 shows a further modified suction box cover of the invention in a fragmentary perspective view.

Referring now to the drawing in detail, and initially to FIG. 1, there is shown as much of a suction box cover of a paper machine as is needed for an understanding of the invention.

The suction box cover includes a supporting plate 16 extending over the entire width of the paper machine. Grooves 17, 15 elongated transversely to the direction of travel of the non-illustrated, cooperating Fourdrinier wire alternate in the surface of the plate in that direction and are of rectangular cross section. Drainage ducts 26 extend downward from each groove through the plate 16 for drawing air and white water from the paper web on the moving Fourdrinier. Each groove 17 receives an elongated contact unit 10 according to the invention which includes as many longitudinally juxtaposed sections 1 of sintered aluminum oxide as are needed to make the contact unit 10 as long as the associated groove 17. They are secured to the plate 16 in a manner presently to be described.

FIG. 2 shows an elongated contact element 10 in cross section on a scale greater than that of FIG. 1. It includes an aluminum alloy channel 2 as long as the associated groove 17. The web of the channel is horizontal in the illustrated Operating position, and the two flanges 7 are perpendicular to the web. All surfaces of the channel 2 are flat. The cavity 4 in the channel 2 is upwardly closed by the abuttingly juxtaposed sections 1 of which only one is visible in FIG. 2.

An integral rib 3 depends from the bottom face of each section 1 into the cavity 4, and the remainder of the cavity is practically completely filled with a body 5 of cured epoxy resin which embeds the rib 3. The rib 3 flares somewhat from the section 1 toward the web of the channel 2 so that the section 1 is firmly interlocked with the resin body 5 which in turn adheres to the aluminum alloy channel. The longitudinal edges of the aluminum oxide section 1 project beyond the flanges 7 for engagement with the lands of the plate 16 between the grooves 17, 25, as is best seen in FIG. 1.

The contact elements 10 in the cover of FIG. 1 are held in their operative positions by gravity and by the slightly smaller than the corresponding dimension of the channel 2, 7 received therein so that the location of the exposed top face of the section l'is determined uniquely by the level of the afore-mentioned lands of the plate 16 and by the thickness of the section 1 exclusive of the rib 3.

The control element shown in FIG. 2 is made from sintered aluminum oxide blanks having the approximate shape shown. The exposed top surface and extreme lateral portions of the bottom surface are ground to a smooth finish and a precise thickness. The rib 3 and adjacent portions of the bottom surface are left in the as-sintered condition, and their roughness enhances the strength of the later bond to the epoxy resin body 5. Shallow grooves on either side of the rib 3 provide an enlarged area of contact with the resin.

The control unit 10 is assembled by juxtaposing the ground, individual ceramic sections 1 in inverted position on a horizontal, flat surface, such as a sheet of plate glass, in a straight row. The inverted channel 2 then is superimposed on the exposed bottom faces of the sections 1, and the cavity 4 between the channel 2 and the row of sections 1 is filled with catalyzed, liquid epoxy composition either by injection under pressure from one longitudinal end of the cavity or through openings in the web part of the channel 2 which are later plugged when the resin cures. It is one of the advantages of epoxy resins that they can be hardened at least partly at ambient temperature. The chemical inertness of the cured epoxy resin to the liquids with which it may come in contact during service is another advantage.

Yet, other initially liquid, self-hardening commercial plastic compositions widely used as potting compounds in the electronic industry have been used successfully, and pilot tests indicate that low-melting metals and alloys may replace the plastic bonding agents. If the bonding material can be protected adequately against attack by white water, lead and its alloys including Woods metal, Rose's metal, and type metal are suitable where their greater weight is not objectionable.

For reasons of weight and cost, aluminum alloys are preferred as the material of construction for the channel 2, and have been found to have adequate corrosion resistance. Under unusual conditions, however, stainless steel or other metal may have to be substituted.

The epoxy resin composition preferably employed is one of the numerous, commercially available grades which are chemically inert to aluminum alloys and aluminum oxide and not affected by the often unavoidable exposure to white water. Fillers and reinforcing members may be incorporated in the resin composition to modify its properties as is conventional in itself and will be discussed more fully hereinbelow.

FIG. 3 shows a modification of the contact element of FIG. 2 in which the mechanical strength of the epoxy resin body 5 is increased by embedded wires 6 of high strength steel or of plastic other than epoxy resin, such as high-strength polyamide.

Movement of the plastic body 5 and of the attached aluminum oxide section 1 vertically outward of the channel 2 is prevented in the elements of FIGS. 2 and' 3 mainly by adhesion of the plastic to the flat walls of the flanges 7. It may be further impeded by mechanical interlocking of the channel with the plastic body 5 in the manner illustrated in FIGS. 4 to 7.

The channel 2' shown in FIG. 4 has flanges 7' of uniform thickness, but provided with longitudinal grooves in their outer faces and corresponding ribs 8 in their inner faces. The ribs 8 project into the resin body 5 to prevent its movement vertically outward of the channel 2'.

An analogous effect is achieved in the contact element illustrated in FIG. 5 by having portions 9 of the flanges 7a adjacent the web of the channel 2a converge away from the web and toward each other at an angle of about 60 before the flanges assume a parallel relationship. An enlarged retaining head 5a is thereby formed on the resin body adjacent the channel web.

A similar result is achieved in the channel 2b shown in FIG. 6 by having the flanges 7, otherwise similar to the flanges shown in FIGS. 2 and 3, converge toward the ceramic sections 1. It will be appreciated that the grooves 17 in the plate 16 illustrated in FIG. 1 may need to be modified in an obvious manner to receive the channels 2', 2a, 2b in adequate conforming engagement.

The channels 2, 2', 2a, 2b are of uniform cross section over their entire lengths and are conveniently prepared by extrusion in a conventional manner. This shaping method lends itself to the production of even more complex cross sectional shapes such as that shown in FIG. 7.

The upper half of the channel 20 has flanges 11 outwardly offset near the channel web to bound longitudinal grooves which receive portions of the resin body 5 and lock the same in position. Additional flanges 12 project downward from the channel web and gradually increase in thickness so that their inner faces bound a downwardly open dove-tailed mortise or groove for engagement with mating tenons or ribs on a support.

The contact elements shown in FIGS. 1 to 7 are employed in suction box covers, and their ceramic sections are of rectangular cross section as is customary. Obviously, they may have different cross sectional shapes when used in other devices which require contact between a wear resistant, hard, stationary element and a traveling Fourdrinier screen or felt of a" paper-type machine.

For use as a foil for wiping water from the underside of the traveling Fourdrinier wire, the sections 1a illustrated in FIG. 8 have an acutely angular front edge 13, as is conventional in itself. The ceramic foil sections la are anchored to a supporting plate member in the manner evident from FIG. 1, or as further modified according to FIGS. 2 to 6. A smoothly rectangular rib 3 has been shown in FIGS. 1, 6, 8, and elsewhere for the sake of simplicity, but it will be understood that the rib 3 flares away from the bottom face of the ceramic section FIG. 10A shows a partial modification of the suction box cover more fully illustrated in FIG. 1. The groove 17 receiving each contact unit communicates with the interior of the suction box through bores 22 in the supporting plate 16. The bottom face 21 of the contact section 1 and the outer faces of the flanges 7 engage the plate 16 with minimal clearance. The height of the channel 2 is slightly smaller than the depth of the groove 17 so that a shallow chamber 23 is formed between the web part of the channel and the bottom of the groove 17. Atmospheric pressure acting on the exposed contact section 1 is thus not balanced by air pressure in the partly evacuated chamber 23 and assists in holding the contact unit in the groove 17.

The coefficients of thermal expansion of sintered aluminum oxide, aluminum alloy, and cured epoxy resin are different. If the paper machine operates-at a temperature which is much above the normal ambient temperature of about C, alternating thermal expansion and contraction of the members in a contact element of the invention may tend to loosen their bond. It is desirable therefore that excessive temperature differences between the ceramic contact sections, the plastic bonding material, and the metallic channel be avoided wherever shown in embodiments of the invention. FIG.

9 shows a contact element of the invention analogous to the devices described hereinabove, but provided with ceramic sections lb having two upwardly flaring side faces 28 as is conventional in contact elements for forming boards.

In the foil assembly illustrated in FIG. 10, one flange 7 of the aluminum alloy channel 2g carries an integral backing plate 30 extending from the free edge of the flange at a right angle to the latter and parallel to the web of the channel. It supports the sharply angular edge portion 13 of a foil section 10 which is thinner than the corresponding foil section 1a shown in FIG. 8. It is fastened to the channel 2g in the same manner as shown in any one of FIGS. 2 to 7, though not explicitly illustrated in FIG. 10.

by providing a path of thermally conductive material between the ceramic material and the metal channel in addition to that provided at the areas of direct contact. The epoxy resin which is the preferred bonding material is normally a thermal insulator, and the rib 3 shown in FIGS. 1 to 11 does not significantly enhance dissipation of thermal energy from the ceramic contact material to the metal channel of the unit and to other metallic elements of the paper machine which could act as heat sinks.

In the modified foil .arrangement illustrated in FIG. 11, the ceramic section 1d is formed on its underside with a dove-tail shaped groove 29 for interlocking engagement with the body 5 of epoxy resin confined in the cavity 4 of a channel 2 identical with that described above with reference to FIGS. 1 to 3. A plate 18 of aluminum alloy is inserted in the cavity 4 and held in position by the solid resin body 5. It is at least approximately parallel to the flanges 7 and approximately equidistant from the flanges, its length being preferably equal to that of the channel 2 and to the width of the paper machine.

he plate 18 reinforces the resin body 5 and is effect1ve 1n reducing the temperature of the ceramic foil section 1d even if its longitudinal edges do not make direct contact with the web of the channel 2 and with the ceramic foil section, as long as it provides a thermally conductive bypass around the epoxy resin. This is of advantage particularly when traveling screens of plastic rather than of bronze wire are employed.

Improved flow of thermal energy from the ceramic contact material to the metallic material of the channel 2 can also be achieved by incorporating a heat conduct ve filler III the bonding plastic. FIG. 12 shows a modification of the device of FIG. 11 for use in a suction bOX cover in which a contact section 1e of generally rectangular cross section is formed with a dove-tail shaped longitudinal groove 29 flaring inw d f h bottom face of the section 1e which seals the cavity 4 of the channel 2 as described above.

The cavity is filled with a solid mixture 5 of cured epoxy resin with chemically resistant, thermally more conductive powdered corundum. Quartz sand i b t equally effective. Metal powders admi d to the resin before curing have generally higher thermal conductivity, but the thermal conductivity required is only of the order of the thermal conductivity of aluminum oxide. It does not-warrant the use of stainless steel or noble metal powder, and other metals, finely divided in the resin, may be attacked over long periods of time.

The ceramic sections such as the afore-described section 1d in which interlocking engagement with the solidified resin body 5 is achieved by means of a dovetailed groove 29 in the bottom face of the ceramic section may be air-cooled or even liquid-cooled if necessary. FIG. 13 shows a modification of the device of FIG. 11 in which the plate 18 is replaced by a flat, rectangular conduit extending across the width of the paper machine, narrow in the direction of wire travel over the ceramic section 1d, and high enough to extend approximately from the horizontal face of the ceramic section 1d in the groove 29 to the web of the associated channel 2. Air may be blown through the conduit 20 for cooling the ceramic section id as well as a screen, particularly a plastic screen, traveling over the section.

The same result is achieved in the otherwise identical embodiment shown in FIG. 14 by an aluminum alloy tube 24 of cylindrical shape received almost entirely in the groove 29. It may be replaced by a tube 24 of rectangular cross section, but similar flow section as is illustrated in FIG. 15. The tubes 24, 24', because of their smaller exposed surfaces, are preferred where water is employed as the cooling medium.

A row of ceramic contact sections, if of sufficient width in the direction of wire travel, may be secured to the support structure by more than one fastening arrangement of the invention, as is shown in FIG. 16.

A ceramic plate section If having an acutely angular leading edge is formed with two dove-tail shaped, spacedly parallel grooves 29 in its bottom face. The section If is mounted on a supporting plate 16' formed with grooves 17 respectively vertically aligned with the grooves 29. A metal plate 18 depends from each groove 29 toward the bottom of the associated groove 17 for conducting heat away from the plate section 1}, and is effective although it does not reach the bottom wall of the groove 17. It is embedded in the resin body 5.

In this embodiment, the function of the channel 2 shown in FIG. 1 is assumed by the walls of the supporting plate 16 which bound the grooves 17.

When paper-type machines originally provided with water extraction apparatus having plastic contact elements are to be equipped with contact elements of hard ceramic or carbide material, the available plastic structure may be modified to provide a support for the contact units of the invention. The relatively soft plastic is readily worked by means of machine tools available in the maintenance shop of many a paper mill. FIGS. 17 to 19 illustrate a plastic suction box cover modified to receive contact units of the invention.

In the modified structure, the original transverse ribs are cut down in height to provide carrier bars 16a which are separated by the suction slots 38 of the original cover and integrally connected by cross members 39. The members 39 are not cut down so that they project upward above the bars 16a, the projecting portion tapering toward a straight edge 39'.

An elongated metal channel 35 is fixedly fastened on the top face of each carrier bar 16a by means of screws 36 passing through elongated slots 37 in the horizontal web of the upwardly open channel 35. Each channel 35 provides a conforming receptacle in which contact units of the invention are received as in the grooves 17 shown in FIGS. 1 and 10A. The specific contact unit shown in FIG. 17 by way of example is the unit more fully described above with reference to FIG. 12, but any other illustrated contact unit having contact sections of hard material and a channel fastened to the contact sections may be employed. In the top plan view of FIG. 18, only one receptacle 35 and a portion of the associated channel 2 have been shown in order to reveal otherwise obscured elements of the suction cover.

The control units may be held in the receptacles 35 by gravity and the non-illustrated, cooperating Fourdrinier wire, as described above, but they may be conveniently anchored in the receptacles 35 in the manner illustrated in FIG. 19. Transverse pins 41 pass through each unit and project laterally from the flanges 7. The receptacles 35 are formed with mating slots 40 in their flange parts. Each slot 40 has a horizontal portion in which the associated pin 41 is movable with clearance, and one end of the slot is upwardly open to permit insertion of the pin 41. When the pins 41 are inserted in the slots 40, the ceramic contact sections 1e are firmly seated on the free top edges of the receptacles 35.

Existing plastic foil assemblies, forming boards, or felt conditioning units may be modified to receive contact units of the invention in mating receptacles in a manner obvious from FIGS. 17 to 19.

FIG. 20 shows a modification of the suction box cover illustrated in FIG. 1 in a perspective side view. The illustrated support for the contact units 10 of the invention is provided by sectional elements 16b held in the operative condition by means of brackets 33 equipped with clamping screws 34 and located near respective sides of the machine. Grooves receiving the contact units 10 are cut into the elements 16b as is shown at 17 in FIG. 1. The walls of the suction grooves 25' are formed by respective faces of two elements 16b, and a suction slot 32 is kept open between the elements by spacers 32 which may be integral with one of the elements 16b.

The effective width of the suction box is reduced by control slides 27 in the terminal portions of the suction slots 32, only one control slide 27 being shown in FIG. 20. The control slides 27 differ from the contact units 10 only by being relatively short. The width of each land between adjacent grooves in the support structure is chosen so that the ceramic contact elements of the control slides 27 are abuttingly engaged with adjacent contact elements of the units 10 in a common plane. No web is formed on the portion of the Fourdrinier screen that travels over the control slides 27, similar slides being provided elsewhere along the path of the screen.

It should be understood, of course, that the foregoing disclosure relates only to preferred embodiments of the invention, and that it is intended to cover all changes and modifications of the examples of the invention herein chosen for the purpose of the disclosure which do not constitute departures from the spirit and scope of the invention set forth in the appended claims.

What is claimed is:

1. A contact unit for a paper-making machine and the like comprising:

a. an elongated channel member having a web part and two flange parts extending from said web part in a common direction,

1. said parts jointly bounding a cavity open in said direction,

2. respective free end portions of said flange parts defining therebetween the open side of said cavy;

b. an elongated contact body constituted by a plurality of elongated contact sections of a material having a hardness greater than 6 on the Mohs scale, 1. said sections being abuttingly juxtaposed in the direction of elongation of said body and having respective top faces located in a common longitudinal plane,

2. each section having two longitudinal bottom face portions transversely spaced from each other,

3. each bottom face portion engaging a respective one of said free end portions in direct contact and partly projecting from the engaged free end portion toward the other bottom face portion,

4. the projecting part of each bottom face portion facing inward of said cavity;

c. a body of bonding material filling said cavity in contact with said channel member and said projecting parts; and

d. a longitudinally elongated, integral rib projecting from one of said bodies and separating said bottom face portions, the other body being formed with a longitudinal groove conformingly receiving said rib.

2. A unit as set forth in claim 1, wherein said channel member consists of metal, and said bonding material is a synthetic resin composition.

3. A unit as set forth in claim 2, wherein said channel member is of uniform cross section over the entire length thereof.

4. A unit as set forth in claim 2, wherein said rib flares in a direction away from said bottom face portions.

5. A unit as set forth in claim 2, wherein said contact body is formed with said groove.

6. A unit as set forth in claim 5, further comprising a metallic member embedded in said body of bonding material, respective portions of said member being received in said groove and offset from said contact sections toward said web part.

7. A unit as set forth in claim 6, wherein said metallic member is plate-shaped, said plate-shaped member being elongated in the direction of elongation of said contact unit.

8. A unit as set forth in claim 2, wherein said body of bonding material is formed with said groove.

9. A unit as set forth in claim 2, wherein the surfaces of said bottom face portions engaging said free end portions are smoother than the surface of another part of each contact section in contact with said body of bonding material in'said groove. 

1. SAID SECTIONS BEING ABUTTINGLY JUXTAPOSED IN THE DIRECTION OF ELONGATION OF SAID BODY AND HAVING RESPECTIVE TOP FACES LOCATED IN A COMMON LONGITUDINAL PLANE,
 1. A CONTACT UNIT FOR A PAPER-MAKING MACHINE AND THE LIKE COMPRISING: A. AN ELONGATED CHANNEL MEMBER HAVING A WEB PART AND TWO FLANGE PARTS EXTENDING FROM SAID WEB PART IN A COMMON DIRECTION;
 1. SAID PARTS JOINTLY BOUNDING A CAVITY OPEN IN SAID DIRECTION,
 2. RESPECTIVE FREE END PORTIONS OF SAID FLANGE PARTS DEFINING THEREBETWEEN THE OPEN SIDE OF SAID CAVITY; B. AN ELONGATED CONTACT BODY CONSTITUTED BY A PLURALITY OF ELONGATED CONTACT SECTIONS OF A MATERIAL HAVING A HARDNESS GREATER THAN 6 ON THE MOHS SCALE,
 2. EACH SECTION HAVING TWO LONGITUDINAL BOTTOM FACE PORTIONS TRANSVERSELY SPACED FROM EACH OTHER,
 2. A unit as set forth in claim 1, wherein said channel member consists of metal, and said bonding material is a synthetic resin composition.
 2. each section having two longitudinal bottom face portions transversely spaced from each other,
 2. respective free end portions of said flange parts defining therebetween the open side of said cavity; b. an elongated contact body constituted by a plurality of elongated contact sections of a material having a hardness greater than 6 on the Mohs scale,
 3. A unit as set forth in claim 2, wherein said channel member is of uniform cross section over the entire length thereof.
 3. EACH BOTTOM FACE PORTION ENGAGING A RESPECTIVE ONE OF SAID FREE END PORTIONS IN DIRECT CONTACT AND PARTLY PROJECTING FROM THE ENGAGED FREE END PORTION TOWARD THE OTHER BOTTOM FACE PORTION,
 3. each bottom face portion engaging a respective one of said free end portions in direct contact and partly projecting from the engaged free end portion toward the other bottom face portion,
 4. A unit as set forth in claim 2, wherein said rib flares in a direction away from said bottom face portions.
 4. THE PROJECTING PART OF EACH BOTTOM FACE PORTION FACING INWARD OF SAID CAVITY; C. A BODY OF BONDING MATERIAL FILLING SAID CAVITY IN CONTACT WITH SAID CHANNEL MEMBER AND SAID PROJECTING PARTS; AND D. A LONGITUDINALLY ELONGATED, INTEGRAL RIB PROJECTING FROM ONE OF SAID BODIES AND SEPARATING SAID BOTTOM FACE PROTIONS, THE OTHER BODY BEING FORMED WITH A LONGITUDINAL GROOVE CONFORMINGLY RECEIVING SAID RIB.
 4. the projecting part of each bottom face portion facing inward of said cavity; c. a body of bonding material filling said cavity in contact with said channel member and said projecting parts; and d. a longitudinally elongated, integral rib projecting from one of said bodies and separating said bottom face portions, the other body being formed with a longitudinal groove conformingly receiving said rib.
 5. A unit as set forth in claim 2, wherein said contact body is formed with said groove.
 6. A unit as set forth in claim 5, further comprising a metallic member embedded in said body of bonding material, respective portions of said member being received in said groove and offset from said contact sections toward said web part.
 7. A unit as set forth in claim 6, wherein said metallic member is plate-shaped, said plate-shaped member being elongated in the direction of elongation of said contact unit.
 8. A unit as set forth in claim 2, wherein said body of bonding material is formed with said groove.
 9. A unit as set forth in claim 2, wherein the surfaces of said bottom face portions engaging said free end portions are sMoother than the surface of another part of each contact section in contact with said body of bonding material in said groove. 